In a typical radio communications network, wireless terminals, also known as mobile stations and/or user equipment (UEs), communicate via a Radio Access Network (RAN) to one or more core networks. The RAN covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” or “eNodeB”. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole mobile network is also broadcasted in the cell. One base station may have one or more cells. The base stations communicate over the air interface operating on radio frequencies with the UE within range of the base stations.
A Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA). In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some versions of the RAN as e.g. in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base station nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations nodes, e.g. eNodeBs in LTE, and the core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio base station nodes without reporting to RNCs.
Increased traffic levels and end-user expectations around data rates and latency are some of the parameters that drive a network change. Mobile broadband operators are updating their networks to enable higher speeds and higher bandwidth by adding more frequency bands to existing macro site, and if that is not enough densifying macro cells and deploying other small cell scenarios.
In urban city streets and squares, outdoor micro cells are attractive, as they have sufficient power both to cover a sizeable outdoor area and reach indoor users on lower floors of buildings. If a fiber line is available for carrying data transmissions, micro Remote Radio Units (RRU) may be deployed. For small indoor hotspots such as cafés, where stand-alone Wi-Fi is often already deployed, and so sites are available, operators may deploy indoor pico Radio Base Stations (pRBS), backhauled over an available fixed broadband. In certain in-building situations—such as stadiums, shopping malls, train stations, airports and offices a mix of cell types may be used, depending of the nature of the building and on the backhaul available. Fiber networks in combination with other networks, e.g. wireless communication networks are becoming more and more common. One particular example of such a combination is to connect a standard base station to a distributed antenna system by means of passive or active components. In an example, optical fiber connects the base station to a remote unit which in turn connects to the antennas. Fiber cabling enables the use of RRUs, pRBS and also the recently proposed architecture ‘Fiber to the Radio head’ (FTTRh), where a radio head is detached from the RBS and a fiber line reaches the radio head also called antenna radio head. The radio head being a unit for transmitting signals over the air to/from a user equipment. In this case, analogue transmission is considered between the radio head (Rh) and RBS to save in complexity and costs.
Optical Line Supervision (OLS) relates to a set of capabilities or parameters for the measurement and reporting of the state of an optical link, such as a fiber line, as defined in the ITU-T Recommendation G.984.2 Amendment 2, e.g. Transceiver temperature of an optical line termination (OLT) and optical network termination (ONT); Transceiver voltage of OLT and ONT; Laser bias current of OLT and ONT; OLT transmit power; OLT receive power per ONT; ONT transmit power; ONT receive power. OLT is a device that terminates the common (root) endpoint of an Optical Distribution Network (ODN), implements a Passive Optical Network (PON) protocol and adapts PON Packet Data Units (PDU) for uplink communications over the provider service interface. The OLT provides management and maintenance functions for the subtended ODN and optical network units (ONU). ONT is a single subscriber device that terminates any one of the distributed (leaf) endpoints of an ODN, implements a PON protocol, and adapts PON PDUs to subscriber service interfaces. An ONT is a special case of an ONU. An ONU is generic term denoting a device that terminates any one of the distributed (leaf) endpoints of an ODN, implements a PON protocol, and adapts PON PDUs to subscriber service interfaces. In some contexts, an ONU implies a multiple subscriber device.
It is the purpose of the ITU-T Recommendation G.984.2 Amendment 2 to describe the physical layer measurements to support OLS capability. In any ODN systems, physical monitoring for OLS may be used for: a) normal status monitoring: get and buffer ‘historic’ data as a reference in a normally working system; b) degradation detection: find the potential faults before they become service-affecting, and identify the source of the problem, e.g., ODN, Optical Backend Terminal (OBT) or Optical Front end Terminal (OFT); c) fault management: detect, localize and diagnose faults.
For wireless networks, two physical layer parameters that read the received or transmitted powers are standardized, Received Signal Strength Indicator (RSSI) and Transmitted Signal Strength Indicator (TSSI). As for optical networks, in a wireless network, RSSI/TSSI may be used for: a) normal status monitoring: get and buffer ‘historic’ data as a reference in a normally working system; b) degradation detection: find the potential faults before they become service-affecting, and identify the source of the problem; c) fault management: detect, localize and diagnose faults. Existent monitoring solutions are focused on data transmissions in the optical domain and are not very efficient nor very accurate in an FTTRh communications network.